iOS7 - Why is CGAffine Transform working properly on iOS8 but not iOS7?

Question

I am having a problem when using CGAffineTransformMakeTranslation on iOS7. The view I am using the CGAffineTransformMakeTranslation is going to a different position when running iOS7 and iOS8. Why is this and what am I doing wrong?

I have a view that I am calling "hud" that is the length of its parentView and 125.0 tall. I am using Auto Layout and here is a screenshot of my story board so you can see how I have the constraints set up. The container view is a collection view of photos.

I have the "hud" hide right away with a transform downward and when a photo is selected it will slide back up into view.

-(void)showHud:(BOOL)show
{
    NSLog(@"Frame Height: %f", hud.frame.size.height);

    if (show && !hudSelectionMode)
    {
        [UIView animateWithDuration:0.5 delay:0 options:0
                     animations:^{
                         hud.transform = CGAffineTransformMakeTranslation(0, 0);
                         hud.alpha = 0.8f;
                     }
                     completion:^(BOOL finished){
                     }
     ];

    }
    else if (!show && !hudSelectionMode)
    {

    [UIView animateWithDuration:0.5 delay:0 options:0
                     animations:^{
                         hud.transform = CGAffineTransformMakeTranslation(0, hud.frame.size.height);
                         hud.alpha = 0.8f; // will be 0.0 when not testing
                     }
                     completion:^(BOOL finished){
                     }
     ];


    }

}

Here is the problem On iOS8 this works flawlessly the hud is hidden from the start and will slide up when an image is selected:

However when running on iOS7 devices the hud is not where I would expect it to be:

If I comment out all the code in -(void)showHud:(BOOL)show the hud will sit at the bottom of the parentView where I would expect it to on both 7 and 8.

Answer 1

On iOS7 you need to multiply the translation value by the scaleFactor of the device. On iOS8 this seems to be done automatically, but not on iOS7.